textproduct: Rapid City

KEY MESSAGES

- Marginal to slight (1-2 out of 5) risk of severe thunderstorms this afternoon/evening with the primary risk of damaging winds, but large hail may also occur - Hot weather (Sunday looks hottest) will continue through Monday with a Heat Advisory through early this evening - Active thunderstorms possible Thursday/Friday, then perhaps a lull for the weekend, and then back to active for early next week

DISCUSSION

(This Afternoon Through Tuesday) Issued at 1106 AM MDT Wed Jul 29 2026

16z surface analysis had trough from eastern MT to central CO. Water vapour loop had upper ridge from NM into eastern MT/WY with a couple of ridge-riders over southeast MT and western WY/UT. 0.5km 1-minute visible satellite loop showed most activity was elevated at this point, although there is a CU field over south- central SD associated with oppressive Td/s in the lower 70s. Effects of these features the main short term forecast concern.

This afternoon/tonight, heat indices will be in the lower 100s east of the Black Hills so hoisted a Heat Advisory earlier to account. Main shortwave rotates around upper ridge later this afternoon and evening. At least 1-2KJ/kg MLCAPE pools ahead of surface trough with 25-35kts of effective shear forecast. Bufkit soundings suggest damaging winds would be the main threat with severe convection (marginal to slight (1-2 out of 5)) risk over CWA, highest over northwestern SD. Latest CAMs/HREF emphasize this thinking. So, expect a couple clusters of severe convection this afternoon/evening moving across the CWA. If cold pools can congeal, could see a line of severe thunderstorms for a period which some CAM solutions suggest. Activity will weaken overnight, but decent low level jet likely to sustain convection. Temperatures will be near guidance.

Thursday, compact mid-level circulation moves across the CWA with continued chances for thunderstorms as a cold front slices through the area leading to "cooler" temperatures. Cold front may be focus for active/severe thunderstorms Thursday afternoon over south-central SD. Temperatures will be near guidance.

Lingering PoPs Friday given way to robust thermal ridge expansion for the weekend with Sunday highs from 100-110F putting pressure on some records. Mostly dry, but it is the northern Plains, so thunderstorms cannot be completely ruled out. Next week looks "cooler" as upper ridge flattens and west/northwest flow aloft develops, sure to provide shortwaves to create daily chances of thunderstorms. Confidence is growing for the brief cooldown.

AVIATION

(For the 18Z TAFS Through 18Z Thursday) Issued At 1126 AM MDT Wed Jul 29 2026

Scattered TSRA will develop this afternoon, impacting northeast WY first around 22Z. The boundary will move east, reaching SD in the evening. SD storms will last into the night, and WY will get a second more subtle round of TSRA overnight as well. For all storms, the primary impact will be strong gusty winds. MVFR conditions may be possible in/near the strongest storms.

FIRE WEATHER

Issued At 1106 AM MDT Wed Jul 29 2026

Elevated fire weather conditions are expected this week due to hot temperatures as well as minimum relative humidity in the teens and 20s. Hotter weather develops for the weekend with even drier air (MinRH as low as 8%), so critical fire weather conditions are likely. Thunderstorm chances highest this afternoon through Friday and then early next week. The cores of thunderstorms that occur through Friday should contain wetting rain, but lightning strikes outside of the cores as well as strong, erratic winds may create opportunities for new fires.

UNR WATCHES/WARNINGS/ADVISORIES

SD...Heat Advisory until 7 PM MDT /8 PM CDT/ this evening for SDZ002- 013-014-031-032-042-043-046-049-073-077-078. WY...None.